U.S. stocks fell, after the Standard & Poor™s 500 Index posted its first back-to-back weekly retreat since October, as the continuing selloff in crude pulled down energy shares before the start of corporate earnings.

Energy shares tumbled 2.7 percent, the most among 10 groups in the S&P 500, as crude dropped 4 percent. Tiffany & Co. lost 12 percent after the jewelry retailer lowered its annual forecast after sales declined during the holiday. SanDisk Corp. fell the most in almost six months after reporting preliminary results below its own estimates.

The S&P 500 slid 0.6 percent to 2,032.30 at 12:10 p.m. in New York. Losses accelerated after the market™s open as the benchmark gauge fell through its average price for the past 50 days. The Dow Jones Industrial Average lost 67.18 points, or 0.4 percent, to 17,670.19. Trading in S&P 500 companies was 4.8 percent above the 30-day average for this time of the day.

The index lost 0.7 percent last week, following a 1.5 percent drop the prior week, amid concern over sliding oil prices, falling U.S. wages and that the European Central Bank™s bond-buying plan won™t be enough to combat deflation.

Investors were whipsawed during the week as the S&P 500 had up and down swings of more than 1 percent on three separate days, with an average daily move of 1.3 percent for the full week. The volatility stands in contrast to 2014, when the gauge fluctuated 0.53 percent on average each day for the calmest year in U.